The present invention relates to apparatus and to a method for carrying out optical analysis of samples and is applicable in particular to the analysis of biological, chemical and biochemical samples.
Many chemical, biochemical and biological assays rely upon inducing a change in the optical properties of a biological sample being tested. For example, in order to test for the presence of an antibody in a blood sample, possibly indicating a viral infection, an enzyme-linked immunosorbent assay (ELISA) can be carried out which produces a visible coloured deposit if the antibody is present. An ELISA makes use of a surface which is coated with an antigen specific to the antibody to be tested for. Upon exposure of the surface to the blood sample, antibodies in the sample bind to the antigens. Subsequent staining of the surface with specific enzyme-conjugated antibodies and reaction of the enzyme with a substrate produces a precipitate which shows up the level of antigen binding and hence allows the presence of antibodies in the sample to be identified. This identification is usually carried out using a light microscope which allows an area of the substrate to be viewed by an operator.
In addition to colour staining using an ELISA, techniques such as fluorescence and gold labelling can be used to alter the optical properties of biological antigen material. Similar techniques are also used in general histology to visualise specific areas of tissue, e.g. particular cell types or cell structures, as well as in cell culture.
A significant disadvantage of existing optical analysis techniques is that they are open to human error because of their subjective nature. These techniques are also not suited to uses where a high throughput of samples is required, for example in blood screening applications or cervical smear tests, and are thus relatively expensive to use. The cost factor is exacerbated because, more often than not, different equipment is required for each particular technique.
An object of the present invention is to provide a technique for carrying out the optical analysis of samples which overcomes or at least mitigates certain of these disadvantages.
It is also an object of the present invention to provide an optical analysis technique which allows high speed automatic analysis of biological, biochemical and chemical samples and which is versatile enough to allow it to be used for a variety of different studies.
These objects are achieved by adapting the technology which has been developed in the field of audio and video compact discs to scan surfaces, to which a sample has been attached, using a light beam which is substantially focused onto that surface. A detector is arranged to detect light reflected from, or transmitted through that surface, and to determine from analysis of the detected light whether the light beam has been interfered with by the sample material.
According to a first aspect of the present invention there is provided a method of conducting an optical inspection of a biological, chemical, or biochemical sample, the method comprising the steps of:
supporting the sample on a substrate; directing a beam of electromagnetic radiation from a radiation source onto the substrate;
scanning the beam over the substrate by rotating the substrate about an axis substantially perpendicular to the substrate and by moving the radiation source in a direction having a component radial to said axis; and
detecting radiation reflected from and/or transmitted through the substrate and sample and providing an output signal corresponding to the detected radiation.
According to a second aspect of the present invention there is provided a system for automatically carrying out an optical inspection of a sample to determine whether or not the sample comprises material which interferes with incident electromagnetic radiation, the system comprising:
a substrate having a surface for supporting the sample;
a source of electromagnetic radiation for providing a beam of electromagnetic radiation;
means for scanning said beam across said surface of the substrate; and
detector means which in use is arranged to detect electromagnetic radiation reflected from and/or passing through the substrate and the sample, the substrate being provided with distributed electromagnetic radiation modulating means for modulating at least a part of said beam with a digitally encoded position address indicative of the location on said surface on which the beam is currently directed, the detector means being arranged to decode the modulated electromagnetic radiation beam to determine the encoded address and to determine if the received beam has been modulated by any of said material which may be present in the sample.
The present invention enables the rapid scanning of a surface coated with components from a sample to determine their presence and also if necessary their optical properties. The system is particularly suited for carrying out the automatic inspection of samples with a high throughput. Moreover, prevision of address information in or on the substrate enables the precise position of the electromagnetic radiation beam on the surface to be determined which in turn allows the accurate mapping of optical data, corresponding to attached material, to the surface. This enables regions of interest on the surface to be easily and quickly relocated.
The present invention is suited to carrying out ELISA where the specific antigen is coated onto the surface of the substrate. The surface is then exposed to the analyte and subsequently the specific enzyme and the resulting sample scanned to detect and quantify the enzyme linked to the surface. The system is also suited to carrying out histological analysis and to the quantitative study of gels run using electrophoresis.
Preferably, the electromagnetic radiation is light, e.g. infra-red, visible or ultra-violet.
According to a third aspect of the present invention there is provided a system for automatically carrying out an optical inspection of a sample to determine whether or not the sample comprises material which interferes with incident electromagnetic radiation, the system comprising:
a substantially planar substrate having a surface for supporting the sample;
a source of electromagnetic radiation for providing, a beam of electromagnetic radiation;
means arranged on one side of the substrate for scanning the beam across the surface of the substrate;
a first detector for detecting electromagnetic radiation reflected from the substrate and the sample;
a second detector for detecting electromagnetic radiation passing through the substrate and the sample; and
control means coupled to the first and second detectors and for causing said beam to scan the surface of the substrate in dependence upon one or both of the outputs of the detectors and for detecting the presence of said components.
In a preferred embodiment of the above second aspect of the present invention the control means is arranged to determine the difference between output signals provided by said first and second detectors, which are representative of the signals detected, for the purpose of detecting said material without signal artifacts arising from, for example, dirt present on the side of the substrate opposite the support surface. The substrate may be provided with distributed address means for modulating the light beam with digitally encoded position information indicative of the area currently being scanned by the light beam, one or other of the detectors being arranged to decode the received light signal to determine the address of the location on which the light beam is incident.
According to a fourth aspect of the present invention there is provided a system for automatically carrying out an optical inspection of a sample to determine whether or not the sample comprises material which interferes with incident electromagnetic radiation, the system comprising:
a disc comprising a plastic base layer on the upper surface of which is formed a plurality of perturbations, for interfering with incident electromagnetic radiation, representing digitally encoded data, and a surface for supporting the sample;
disc reading apparatus including a source of electromagnetic radiation for providing a beam of electromagnetic radiation, scanning means for scanning the beam across the upper surface of the disk, and an electromagnetic radiation detector for detecting radiation reflected from and/or transmitted through the disk and said sample components; and
means for rotating the disc about an axis substantially perpendicular to said beam,
wherein, in addition to being modulated by information digitally encoded onto the disc, the beam is additionally modulated by any of said material which is attached to the support surface of the disc.
Preferably, said electromagnetic radiation is visible light although infra-red or ultra-violet radiation may be suitable.
Preferably, the disc comprises a lower layer of transparent plastic on the surface of which is impressed, or otherwise produced, said digital information. This surface is coated with a partially reflective layer, for example of aluminium, which in turn may be covered by a further layer of transparent plastic.
In an embodiment of the above fourth aspect of the invention the upper surface of the disc is provided with a 3D surface topology arranged to provide growth and attachment cues for cells grown on the surface. For example, the surface may be provided with a rectangular grating for causing cells to align in a chosen direction. Alternatively, growth and attachment cues may be provided by chemical patterning of the surface, e.g. using fibrenectin, produced, for example, using photolithography.
In another embodiment of the above fourth aspect of the present invention the upper surface of the disc is coated with a gel suitable for carrying out electrophoresis on proteins, DNA etc. In order to run the gels radially, a first electrode may be provided at the centre of the disc with a second electrode being provided around the periphery of the disc. A well may be formed in the gel into which the analyte can be placed.
In order to calibrate a system embodying the present invention, the disc may be provided with a calibration track, e.g. a series of 256 grey levels. These levels may be printed onto the surface of the track using an ink jet printer.
According to a fifth aspect of the present invention there is provided a substrate for use in a system which is arranged to carry out an optical inspection on the substrate to determine whether or not material which interferes with incident electromagnetic radiation is present on a surface of the substrate, the substrate including a preformed calibration scale which enables calibration of said system.
Preferably, the calibration scale is a series of graded grey regions which reflect or transmit light to varying degrees. This scale may be printed on a surface of the substrate using an ink jet printer.
According to a sixth aspect of the present invention there is provided apparatus for conducting an optical inspection of a biological, chemical, or biochemical sample supported on a substrate, the apparatus comprising;
means for supporting a substrate and for rotating the substrate about an axis substantially perpendicular to the substrate;
a source of electromagnetic radiation for providing a beam of electromagnetic radiation;
drive means for moving the radiation source over the mounted sample in a direction having a component radial to said axis so that in combination with the means for rotating the substrate the radiation beam can be scanned over the substrate; and
detector means for detecting radiation reflected from or transmitted through the substrate and sample and for providing an output signal corresponding to the detected radiation.